U.S. patent number 11,398,355 [Application Number 17/038,740] was granted by the patent office on 2022-07-26 for perovskite silicon tandem solar cell and method for manufacturing the same.
This patent grant is currently assigned to SEOUL NATIONAL UNIVERSITY R&DB FOUNDATION. The grantee listed for this patent is SEOUL NATIONAL UNIVERSITY R&DB FOUNDATION. Invention is credited to You Jin Ahn, Su Geun Ji, Jin Young Kim, Ik Jae Park.
United States Patent |
11,398,355 |
Kim , et al. |
July 26, 2022 |
Perovskite silicon tandem solar cell and method for manufacturing
the same
Abstract
Disclosed is a tandem solar cell according to an aspect
including: a silicon lower cell; a perovskite upper cell disposed
on the silicon lower cell; and a bonding layer for bonding the
silicon lower cell and the perovskite upper cell between the
silicon lower cell and the perovskite upper cell, wherein the front
surface portion of the silicon lower cell being in contact with the
bonding layer includes a texture structure, the bonding layer
includes a first transparent electrode layer formed on the sidewall
of the texture structure, a buried layer filling concave portions
of the texture structure on the first transparent electrode layer,
and a second transparent electrode layer on top surfaces of the
buried layer, the first transparent electrode layer and the texture
structure.
Inventors: |
Kim; Jin Young (Seoul,
KR), Park; Ik Jae (Seoul, KR), Ji; Su
Geun (Ulsan, KR), Ahn; You Jin (Seoul,
KR) |
Applicant: |
Name |
City |
State |
Country |
Type |
SEOUL NATIONAL UNIVERSITY R&DB FOUNDATION |
Seoul |
N/A |
KR |
|
|
Assignee: |
SEOUL NATIONAL UNIVERSITY R&DB
FOUNDATION (Seoul, KR)
|
Family
ID: |
1000006453740 |
Appl.
No.: |
17/038,740 |
Filed: |
September 30, 2020 |
Prior Publication Data
|
|
|
|
Document
Identifier |
Publication Date |
|
US 20210098201 A1 |
Apr 1, 2021 |
|
Foreign Application Priority Data
|
|
|
|
|
Oct 1, 2019 [KR] |
|
|
10-2019-0121867 |
Sep 3, 2020 [KR] |
|
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10-2020-0112556 |
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L
31/02363 (20130101); H01L 27/302 (20130101); H01L
31/1888 (20130101); H01L 51/4213 (20130101); H01L
31/0543 (20141201); H01G 9/20 (20130101); H01L
51/4246 (20130101) |
Current International
Class: |
H01G
9/20 (20060101); H01L 31/054 (20140101); H01L
51/42 (20060101); H01L 31/0236 (20060101); H01L
31/18 (20060101); H01L 27/30 (20060101) |
Field of
Search: |
;136/243-265 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
Choi et al, Two-terminal mechanical perovskite/silicon tandem solar
cells with transparent conductive adhesives, Aug. 2019, Nano
Energy, vol. 65, 104044, 1-10. (Year: 2019). cited by examiner
.
Choi Master's Thesis, Study on Optimal Device Design for 2-terminal
Mechanical Perovskite/Silicon Tandem Solar Cells with Transparent
Conductive Adhesives, Sep. 2019, Ulsan Graduate School of UNIST.
(Year: 2019). cited by examiner .
JP-2010232563-A English machine translation (Year: 2010). cited by
examiner.
|
Primary Examiner: Golden; Andrew J
Attorney, Agent or Firm: Kilpatrick Townsend & Stockton
LLP
Claims
What is claimed is:
1. A tandem solar cell comprising: a silicon lower cell; a
perovskite upper cell disposed on the silicon lower cell; and a
bonding layer for bonding the silicon lower cell and the perovskite
upper cell between the silicon lower cell and the perovskite upper
cell, the front surface portion of the silicon lower cell being in
contact with the bonding layer includes a texture structure,
wherein the texture structure comprises concave-convex structures
which have lateral faces and top faces, the bonding layer includes
a first transparent electrode layer formed on the lateral faces of
the concaves, a buried layer filling concaves of the texture
structure on the first transparent electrode layer, wherein
portions of the first transparent electrode layer is exposed
between the texture structure and the buried layer and a second
transparent electrode layer on top surfaces of the buried layer,
directly contacting the exposed first transparent electrode layer
and the texture structure, wherein the top surfaces of the buried
layer, the first transparent electrode layer and the texture
structure form a flat plane.
2. The tandem solar cell of claim 1, wherein the texture structure
has a size in the range of 0.1 .mu.m to 20 .mu.m.
3. The tandem solar cell of claim 1, wherein each of the first
transparent electrode layer and the second transparent electrode
layer independently includes aluminum zinc oxide (AZO), indium tin
oxide (ITO), fluorine doped tin oxide (FTO), or indium zinc oxide
(IZO).
4. The tandem solar cell of claim 1, wherein the buried layer
includes a thermally curable or photocurable polymer material.
5. The tandem solar cell of claim 1, wherein the buried layer
comprises an epoxy resin, an acryl resin, a siloxane resin, or a
vinyl acetate resin.
6. The tandem solar cell of claim 1, further comprising: a lower
electrode connected to the silicon lower cell; and an upper
electrode connected to the perovskite upper cell.
Description
CROSS-REFERENCE TO RELATED APPLICATION
This application is based on and claims priority under 35 U.S.C.
.sctn. 119 to Korean Patent Application No. 10-2019-0121867, filed
on Oct. 1, 2019, and Korean Patent Application No. 10-2020-0112556,
filed on Sep. 3, 2020 in the Korean Intellectual Property Office,
the disclosures of which are incorporated by reference herein in
their entireties.
BACKGROUND
1. Field
The present disclosure relates to a tandem solar cell including a
silicon lower cell and a perovskite upper cell and a method for
manufacturing the same.
2. Description of Related Art
A solar cell is an environmentally-friendly device that converts
solar energy into electric energy. Photovoltaic power generation is
enabled when sunlight is absorbed into a light absorbing layer of a
solar cell and electron-hole pairs are generated. Only the incident
sunlight having a bandgap greater than the light absorbing layer is
absorbed into the light absorbing layer, and the energy of the
incident sunlight having a bandgap not greater than that of the
light absorbing layer is consumed as thermal energy. Therefore, in
order to efficiently utilize sunlight, tandem solar cells employing
a multitude of light absorbing layers having different bandgaps are
receiving much attention.
Perovskite materials currently receiving much attention as light
absorbing layer materials for next-generation solar cells are
capable of easily adjusting bandgaps and efficiently distributing
incident light with respect to a lower cell of the thin film solar
cell when the light absorbing layer is bonded to the lower cell
made of, for example, a silicon, copper indium gallium selenide
(CIGS), or copper zinc tin sulfide (CZTS). In addition, the
perovskite material is capable of forming a thin film using a
low-temperature solution process, and thus the manufacturing cost
may be reduced.
In order to reduce reflection of incident light, the silicon solar
cell of the lower cell employs a pyramidal texture structure on its
front surface portion, and the size of the texture structure is
generally in micrometer (.mu.m) scales. Meanwhile, the perovskite
light absorbing layer of the upper cell has a thickness of several
hundred nanometers, and it is difficult to uniformly form layers
with such a thickness scale on the micrometer-scale texture
structure using a solution process.
Therefore, the tandem device including a perovskite upper cell
using the conventional solution process and a silicon lower cell
having a texture structure may have a reduced photoelectric
conversion efficiency due to a non-uniformly formed perovskite
light absorbing layer. Meanwhile, in the tandem device including a
perovskite upper cell using the conventional solution process and a
silicon lower cell without a texture structure, a uniform
perovskite layer may be formed in the upper cell, but the loss of
light may be unavoidably generated due to the front surface
reflection of the silicon lower cell.
SUMMARY
In order to solve the problems occurring in the prior art, the
present disclosure provides a silicon perovskite tandem solar cell
capable of uniformly forming a light conversion layer in a
perovskite upper cell on a texture structure of a silicon lower
cell using a solution process, and a method for manufacturing the
same.
Additional aspects will be set forth in part in the description
which follows and, in part, will be apparent from the description,
or may be learned by practice of the presented embodiments of the
disclosure.
According to an aspect, provided is a tandem solar cell.
The solar cell includes:
a silicon lower cell;
a perovskite upper cell disposed on the silicon lower cell; and
a bonding layer for bonding the silicon lower cell and the
perovskite upper cell between the silicon lower cell and the
perovskite upper cell.
The front surface portion of the silicon lower cell being in
contact with the bonding layer may include a texture structure.
The bonding layer may include
a first transparent electrode layer formed on the sidewall of the
texture structure,
a buried layer filling concave portions of the texture structure on
the first transparent electrode layer, and
a second transparent electrode layer on top surfaces of the buried
layer, the first transparent electrode layer and the texture
structure.
The texture structure may have a truncated pyramid shape.
The second transparent electrode layer may be in contact with the
first transparent electrode layer exposed between the texture
structure and the buried layer.
The top surfaces of the buried layer, the first transparent
electrode layer and the texture structure may form a flat
plane.
The texture structure may have a size in the range of sub
micrometers to several tens of micrometers.
Each of the first transparent electrode layer and the second
transparent electrode layer may independently include aluminum zinc
oxide (AZO), indium tin oxide (ITO), fluorine doped tin oxide
(FTO), or indium zinc oxide (IZO).
The buried layer may have a lower refractive index than layers
adjacent thereto.
The buried layer may include a thermally curable or photocurable
polymer material.
The buried layer may include an epoxy resin, an acryl resin, a
siloxane resin, a vinyl acetate resin.
The tandem solar cell may further include a lower electrode
connected to the silicon lower cell, and
an upper electrode connected to the perovskite upper cell.
According to another aspect, provided is a method for manufacturing
the tandem solar cell.
The method for manufacturing the tandem solar cell may include the
steps of:
forming a pre-texture structure by texturing a front surface
portion of a silicon lower cell;
forming a first transparent electrode layer on the pre-texture
structure to a uniform thickness;
forming a buried layer on the first transparent electrode layer to
cover the pre-texture structure;
forming a texture structure by etching top portions of the buried
layer, the first transparent electrode layer and the pre-texture
structure, and exposing top surfaces of the buried layer filling
the concave portions of the texture structure, the texture
structure, and the first transparent electrode layer between the
buried layer and the texture structure;
forming a second transparent electrode layer on the exposed top
surfaces of the buried layer, the first transparent electrode layer
and the texture structure; and
forming a perovskite upper cell on the second transparent electrode
layer.
The top surfaces of the buried layer, the first transparent
electrode layer and the texture structure may form a flat
plane.
The texture structure may have a size in the range of sub
micrometers to several tens of micrometers.
The step of etching the top portions of the buried layer, the first
transparent electrode layer and the texture structure may include
chemical etching, physical etching or chemical mechanical
polishing.
The buried layer may have a lower refractive index than layers
adjacent thereto.
The step of forming the perovskite upper cell may include:
forming an hole transport layer on the second transparent electrode
layer;
forming a perovskite light absorbing layer on the hole transport
layer; and
forming an electron transport layer on the perovskite light
absorbing layer.
The perovskite light absorbing layer may be formed by a solution
process.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other aspects, features, and advantages of certain
embodiments of the disclosure will be more apparent from the
following description taken in conjunction with the accompanying
drawings, in which:
FIG. 1 is a cross-sectional view schematically illustrating a
configuration of a perovskite silicon tandem solar cell according
to an embodiment; and
FIGS. 2A to 2F are schematic cross-sectional views sequentially
illustrating a method for manufacturing a perovskite silicon tandem
solar cell according to an embodiment.
DETAILED DESCRIPTION
Reference will now be made in detail to embodiments, examples of
which are illustrated in the accompanying drawings, wherein like
reference numerals refer to like elements throughout. In this
regard, the present embodiments may have different forms and should
not be construed as being limited to the descriptions set forth
herein. Accordingly, the embodiments are merely described below, by
referring to the figures, to explain aspects of the present
description. As used herein, the term "and/or" includes any and all
combinations of one or more of the associated listed items.
Expressions such as "at least one of," when preceding a list of
elements, modify the entire list of elements and do not modify the
individual elements of the list.
The terminology used herein is for the purpose of describing
particular example embodiments only and is not intended to be
limiting of the present inventive concept. An expression used in
the singular encompasses the expression of the plural, unless it
has a clearly different meaning in the context. As used herein, it
is to be understood that the terms such as "includes," "have," and
"comprise" are intended to indicate the presence of the features,
numbers, steps, actions, components, parts, ingredients, materials,
or combinations thereof disclosed in the specification, but do not
preclude the possibility that one or more other features, numbers,
steps, actions, components, parts, ingredients, materials, or
combinations thereof may exist or may be added.
In the drawings, the diameters, lengths, and thicknesses of layers
and regions are exaggerated or reduced for clarity. Throughout the
specification, it is to be understood that when a component, such
as a layer, a film, a region, or a plate, is referred to as being
"on" another component, the component can be directly on the other
component or intervening components may be present thereon.
Throughout the specification, the terms "first," "second," etc. may
be used to describe various elements, these elements, components,
regions, layers and/or sections should not be limited by these
terms. These terms are only used to distinguish one element from
another element. In addition, throughout the specification and
drawings, an identical or corresponding element will be referred to
as an identical reference numeral, and repeated descriptions will
not be given.
As used herein, a lower cell means a solar cell formed at a lower
portion of a tandem solar cell, and a silicon lower cell means a
solar cell in a case where the solar cell formed at the lower
portion of the tandem solar cell is a silicon solar cell. Likewise,
as used herein, an upper cell means a solar cell formed at an upper
portion of a tandem solar cell, and a perovskite upper cell means a
solar cell in a case where the solar cell formed at the upper
portion of the tandem solar cell is a perovskite solar cell.
As used herein, a texture structure means a structure formed in the
silicon solar cell and may include not only a structure formed by a
general texturing process but also a structure derived
therefrom.
As used herein, a silicon solar cell is a solar cell in which a
light absorbing layer contains silicon and a perovskite solar cell
means a solar cell in which a light absorbing layer contains a
material having a perovskite structure.
As used herein, a perovskite light absorbing layer means a light
absorbing layer including a light absorbing material having a
perovskite structure.
Hereinafter, tandem solar cells according to one or more
embodiments and a method for manufacturing the same will be
described in further detail with reference to the accompanying
drawings.
<Tandem Solar Cell>
FIG. 1 is a cross-sectional view schematically illustrating a
configuration of a perovskite silicon tandem solar cell according
to an embodiment.
Referring to FIG. 1, the perovskite silicon tandem solar cell 100
includes a silicon lower cell 110, a bonding layer 120 and a
perovskite upper cell 130.
The silicon lower cell 110 may have one of known silicon solar cell
structures, but embodiments of the present disclosure are not
limited thereto. In an example embodiment, the silicon lower cell
110 may include a crystalline silicon substrate (not shown), a
p-type amorphous or crystalline silicon layer (not shown), an
n-type amorphous or crystalline silicon layer (not shown), and an
amorphous intrinsic silicon layer (not shown). In addition to the
above-described layers, the silicon lower cell 110 may further
include additional layers as necessary.
The front surface portion of the silicon lower cell 110 being in
contact with the bonding layer 120 may have a texture structure 119
having a truncated pyramid shape. The front surface portion of the
silicon lower cell 110 may be a silicon layer. The texture
structure 119 may have a size in the range of sub micrometers to
several tens of micrometers. In an example embodiment, the texture
structure 119 may have a width and height in the range of 0.1 .mu.m
to 5 .mu.m. The texture structure 119 of the silicon lower cell 110
may reduce the reflection of incident light and increase the path
of the incident light to improve light collection efficiency,
thereby increasing the absorption efficiency of sunlight.
The bonding layer 120 is a layer that physically bonds and
electrically connects the silicon lower cell 110 and the perovskite
upper cell 130 to each other. The bonding layer 120 includes: a
first transparent electrode layer 121 formed on the sidewall of the
texture structure 119 of the front surface portion of the silicon
lower cell 110; a buried layer 123 filling concave portions of the
texture structure 119 so as to expose top surface parts 121a of the
first transparent electrode layer 121; and a second transparent
electrode layer 125 covering top surfaces of the buried layer 123,
the first transparent electrode layer 121 and the silicon lower
cell 110.
The first transparent electrode layer 121 and the buried layer 123
fill the texture structure 119 of the silicon lower cell 110 to
thus planarize the front surface portion of the silicon lower cell
110. The second transparent electrode layer 125 is formed on the
flat top surface of the silicon lower cell 110, which is planarized
by being filled with the first transparent electrode layer 121 and
the buried layer 123. Since the top surface parts 121a of the first
transparent electrode layer 121, exposed to the top surface of the
silicon lower cell 110, are in contact with the second transparent
electrode layer 125, the silicon lower cell 110 is electrically
connected to the second transparent electrode layer 125 through the
first transparent electrode layer 121.
Each of the first transparent electrode layer 121 and the second
transparent electrode layer 125 may independently include a
conductive metal oxide, such as aluminum zinc oxide (AZO), indium
tin oxide (ITO), fluorine doped tin oxide (FTO), or indium zinc
oxide (IZO). In an example embodiment, the first transparent
electrode layer 121 may have a thickness in the range of 5 nm to
300 nm. When the first transparent electrode layer 121 has a
thickness in the range stated above, the first transparent
electrode layer 121 may be formed on the sidewall of the texture
structure 119 to a uniform thickness, and its surface being in
contact with the second transparent electrode layer 125 may be
stably maintained. In an example embodiment, the second transparent
electrode layer 125 may have a thickness in the range of 5 nm to
100 nm. When the first transparent electrode layer 121 and the
second transparent electrode layer 125 have a thickness in the
range stated above, they may be electrically connected to each
other to serve as a recombination layer.
The buried layer 123 may include a transparent material having
refractive index in the range of about 1 to about 3. The buried
layer 123 may include, for example, a thermally curable or
photocurable polymer material. The thermally curable or
photocurable transparent polymer material may include, for example,
an epoxy resin, an acryl resin, a siloxane resin, a vinyl acetate
resin, or a combination thereof, but embodiments of the present
disclosure are not limited thereto. When the buried layer 123 have
the refractive index in the range of about 1 to about 3, the buried
layer 123 may have a refractive index similar to the layers
adjacent thereto. In detail, the buried layer 123 may have a
similar refractive index to the layers forming the silicon lower
cell 110 and the layers forming the perovskite upper cell 130. When
the buried layer 123 has a refractive index similar to the layers
adjacent thereto, the reflection of incident light may be
minimized. Optionally, the buried layer 123 may further include
conductive particles unless the refractive index or transmission
rate is not affected.
The perovskite upper cell 130 disposed on the bonding layer 120 may
have one of known perovskite solar cell structures, and the
structure of the perovskite upper cell 130 is not particularly
limited. In an example embodiment, the perovskite upper cell 130
may include an hole transport layer (not shown), a perovskite light
absorbing layer (not shown), and a electron transport layer (not
shown).
The hole transport layer may include, for example, a conductive
polymer material or a conductive inorganic material. The conductive
polymer material may include, for example, polyaniline,
polypyrrole, polythiophene, poly-3,4-ethylene
dioxythiophene-polystyrene sulfonate (PEDOT-PSS),
poly-[bis(4-phenyl)(2,4,6-trimethylphenyl)amine](PTAA),
spiro-MeOTAD or polyaniline-camphor sulfonic acid (PANI-CSA), but
embodiments of the present disclosure are not limited thereto. The
conductive inorganic material may include NiO, WO.sub.3, or CuSCN,
but embodiments of the present disclosure are not limited thereto.
In an example embodiment, the hole transport layer may have a
thickness in the range of 5 nm to 300 nm.
The light absorbing layer may include a light absorbing material
having a perovskite structure. The light absorbing layer having a
perovskite structure may include, for example, organic halide
perovskite or metal halide perovskite.
The organic halide perovskite may include, for example,
CH.sub.3NH.sub.3Pbl.sub.3, CH.sub.3NH.sub.3Pbl.sub.xCl.sub.3-x,
CH.sub.3NH.sub.3Pbl.sub.xBr.sub.3-x,
CH.sub.3NH.sub.3PbCl.sub.xBr.sub.3-x, HC(NH.sub.2).sub.2Pbl.sub.3,
HC(NH.sub.2).sub.2Pbl.sub.xCl.sub.3-x,
HC(NH.sub.2).sub.2Pbl.sub.xBr.sub.3-x,
HC(NH.sub.2).sub.2PbCl.sub.xBr.sub.3-x,
(CH.sub.3NH.sub.3)(HC(NH.sub.2).sub.2).sub.1- yPbl.sub.3,
(CH.sub.3NH.sub.3)(HC(NH.sub.2).sub.2)1.sub.1-yPbl.sub.xCl.sub.3-x,
(CH.sub.3NH.sub.3)(HC(NH.sub.2).sub.2).sub.1-yPbl.sub.xBr.sub.3-x,
or
(CH.sub.3NH.sub.3)(HC(NH.sub.2).sub.2).sub.1-yPbCl.sub.xCr.sub.3-x(0.ltor-
eq.x.ltoreq.1, 0.ltoreq.y.ltoreq.1), but embodiments of the present
disclosure are not limited thereto. In addition, a compound
partially doped with Cs or Rb in the organic ammonium moiety may
also be used as the organic halide perovskite. The metal halide
perovskite may include, for example, lead iodide (Pbl2), lead
bromide (PbBr) or lead chloride (PbCl2). The light absorbing layer
may have a thickness in the range of several tens to several
hundreds of nanometers. In an example embodiment, the light
absorbing layer may have a thickness in the range of 100 nm to 1000
nm.
The electron transport layer may include, for example, TiO.sub.2,
SnO.sub.2, ZnO, TiSrO.sub.3, graphene, carbon nanotubes,
[6,6]-phenyl-C.sub.61-butyric acid methyl ester (PCBM), or a
combination thereof, but embodiments of the present disclosure are
not limited thereto. In an example embodiment, the electron
transport layer may have a thickness in the range of 1 nm to 300
nm.
In addition to the above-described layers, the perovskite upper
cell 130 may further include additional layers as necessary.
In addition, the perovskite silicon tandem solar cell 100 may
further include a lower electrode (not shown) connected to the
silicon lower cell 110 and an upper electrode (not shown) connected
to the perovskite upper cell 130.
The perovskite silicon tandem solar cell according to the present
embodiment may have an increased absorption efficiency of the
sunlight by reducing the reflection of the sunlight using the
texture structure of the silicon lower cell. In addition, a bonding
layer is planarly formed on the texture structure, thereby forming
the perovskite upper cell reliably.
<Manufacturing Method of Tandem Solar C
ell>
FIGS. 2A to 2E are schematic cross-sectional views sequentially
illustrating a method for manufacturing a perovskite silicon tandem
solar cell according to an embodiment.
First, referring to FIG. 2A, a pre-texture structure 118 may be
formed by texturing a front surface portion of a silicon lower cell
110. The front surface portion of the silicon lower cell 110 may be
a silicon layer. Although not shown in FIG. 2A, as described above,
the silicon lower cell 110 may include a p-type amorphous or
crystalline silicon layer (not shown), an n-type amorphous or
crystalline silicon layer (not shown), and an amorphous intrinsic
silicon layer (not shown), and may have a variety of structures
without being limited thereto. The texturing may be performed
through, for example, etching or grooving. The pre-texture
structure 118 may have, for example, a pyramidal shape. At the time
of etching for texturing, for example, a basic solution, such as
potassium hydroxide (KOH) or sodium hydroxide (NaOH), or an acid
solution, such as nitric acid (HNO3) or fluoric acid (HF). The
grooving for texturing may be performed using, for example, laser.
Meanwhile, a rear surface portion of the silicon lower cell 110 may
have a texture structure or a planar structure.
Referring to FIG. 2B, a first transparent electrode layer 121 may
be formed on the pre-texture structure 118. The first transparent
electrode layer 121 may be made of a conductive metal oxide, such
as, for example, ITO, AZO, FTO, or IZO. The conductive metal oxide
of the first transparent electrode layer 121 may be formed using,
for example, sputtering or spin coating. In an example, the first
transparent electrode layer 121 may be conformally formed to have a
uniform thickness so as to maintain irregularities of the texture
structure 119. In an example embodiment, the first transparent
electrode layer 121 may have a thickness in the range of 5 nm to
300 nm.
Referring to FIG. 2C, a buried layer 123 may be formed on the first
transparent electrode layer 121 so as to cover completely the
pre-texture structure 118 of the silicon lower cell 110. The buried
layer 123 may be made of, for example, a thermally curable or
photocurable polymer material having a refractive index in the
range of about 1 to about 3. The buried layer 123 may be made of,
for example, an epoxy resin, an acryl resin, a siloxane resin, a
vinyl acetate resin, or a combination thereof. Optionally, the
buried layer 123 may further include conductive particles. The
buried layer 123 may be formed to have an appropriate thickness so
as to perform a planarization process on the lower texture
structure 119.
Referring to FIG. 2D, the top surface of the silicon lower cell 110
may be planarized while exposing the first transparent electrode
layer 121, by etching top portions of the buried layer 123, the
first transparent electrode layer 121 and the pre-texture structure
118. During the planarization process, chemical etching, physical
etching or chemical mechanical polishing may be used. In an example
embodiment, a compound or a suspension, including silica, diamond,
alumina or cesium oxide, may be used to perform the chemical
mechanical polishing. The top portion of the pre-texture structure
118 is etched to form a texture structure 119, and the top surface
of the buried layer 123 filling the concave portions of the texture
structure 119 and top surface parts 121a of the first transparent
electrode layer 121 are exposed.
Referring to FIG. 2E, a second transparent electrode layer 125 may
be formed on the texture structure 119, the first transparent
electrode layer 121 and the buried layer 123, which are exposed
after the etching for planarization. The second transparent
electrode layer 125 may include, for example, AZO, ITO, FTO, or
IZO. The second transparent electrode layer 125 may be made of the
same material as the first transparent electrode layer 121.
Optionally, the second transparent electrode layer 125 may be made
of a different material from the first transparent electrode layer
121. The second transparent electrode layer 125 is in contact with
the first transparent electrode layer 121 to then be electrically
connected thereto. The first transparent electrode layer 121, the
buried layer 123 and the second transparent electrode layer 125 may
form a bonding layer 120 connecting the silicon lower cell 110 and
the perovskite upper cell 130. Electrons from the silicon lower
cell 110 and holes from the perovskite upper cell 130 are
recombined at the first transparent electrode layer 121 and the
second transparent electrode layer 125 in the bonding layer 120,
thereby maintaining charge neutrality.
Referring to FIG. 2F, the perovskite upper cell 130 may be formed
on the second transparent electrode layer 125. The perovskite upper
cell 130 may be formed by a publicly known method. Although not
shown in FIG. 2F, the perovskite upper cell 130 may include a hole
transport layer, a light absorbing layer, and an electron transport
layer. As to the hole transport layer, the light absorbing layer
and the electron transport layer according to the present
embodiment, reference may be made to the description of the tandem
solar cell according to the previous embodiment.
In an example embodiment, the hole transport layer, the light
absorbing layer and the electron transport layer may be
sequentially formed on the second transparent electrode layer 125,
thereby forming the perovskite upper cell 130. The hole transport
layer may be formed by, for example, spin coating or thermally
evaporating a conductive polymer or a conductive inorganic material
such as NiO, WO.sub.3 or CuSCN on second transparent electrode
layer 125. The light absorbing layer may be formed on the hole
transport layer using a light absorbing material having a
perovskite structure. The light absorbing layer may be formed by,
for example, spin coating a solution prepared by dissolving a
precursor material of organic halide perovskite or metal halide
perovskite on the hole transport layer. The electron transport
layer may be formed on the light absorbing layer using, for
example, TiO.sub.2, SnO.sub.2, ZnO, TiSrO.sub.3, graphene, carbon
nanotubes or PCBM, by sol-gel method, spin coating or thermal
evaporation. In another example embodiment, the electron transport
layer may be formed on the second transparent electrode layer 125,
and the hole transport layer may be formed on the the light
absorbing layer. According to another embodiment, additional layers
may be further formed when forming the perovskite upper cell
130.
According to embodiments of the present disclosure, the top portion
of the texture structure formed on the front surface portion of the
silicon lower cell may be planarized at the time of forming a
bonding layer, and thus a perovskite upper cell may be easily and
reliably formed at low cost by employing a solution process. The
thus formed perovskite silicon tandem solar cell may have an
increased photoelectric conversion efficiency by forming the
perovskite upper cell reliably while maintaining the texture
structure of the silicon lower cell.
According to the configuration of the perovskite silicon tandem
solar cell and the method for manufacturing the same of the present
disclosure, a perovskite upper cell may be reliably formed on a
silicon lower cell having a texture structure on the front surface
portion thereof using a solution process, and thus the perovskite
silicon tandem solar cell having excellent performance may be
manufactured.
It should be understood that embodiments described herein should be
considered in a descriptive sense only and not for purposes of
limitation. Descriptions of features or aspects within each
embodiment should typically be considered as available for other
similar features or aspects in other embodiments. While one or more
embodiments have been described with reference to the figures, it
will be understood by those of ordinary skill in the art that
various changes in form and details may be made therein without
departing from the spirit and scope of the disclosure as defined by
the following claims.
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